Businesses that rent storage (memory regions secured on a hard disk, or the like) to clients for a price (storage business) have recently developed under the name of storage service provider (SSP). Specifically, the storage service provider side prepares storage that is associated with a server of a client (requesting processing apparatus), and the client requests a necessary volume of the storage from the storage service provider and pays a rental fee in response to the volume he or she requested.
Because clients pay fees corresponding to the storage volume, a wasteful situation where the same data is stored in duplicate is not desirable to them. A duplication elimination technique is for eliminating this kind of waste. Specifically, a duplication elimination technique is a technique by which, when data (referred to as target data hereinafter) is to be stored in storage, whether or not the same data has already been stored in that storage is detected, i.e., the data duplication is detected, and if the same data has already been stored, the target data is replaced by, for example, linking so as to put together the duplicated data into one piece of data (elimination) (See Patent Documents 1 and 2, for example). The name duplication elimination technique is also used to refer to a technique of eliminating all pieces of the same data that have already been duplicated except for one piece of that data.
A duplication elimination system using this kind of a duplication elimination technique divides information in a file or storage into prescribed units, uses a collision-safe hash value such as an encoded hash value, and performs determination of duplication by comparing the hash values. The purpose of this is to avoid duplicate recording of data, and to reduce the volume in a storage system.
This duplication elimination technique can reduce the volume of storage necessary for storing data. Effective utilization of storage such as this leads to suppression of power consumption and a use rate of an installation place.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2009-80671
Patent Document 2: Japanese Laid-Open Patent Publication No. 2011-118712